The present invention relates to a spectroscope for performing tests on a sample of body fluid to be analyzed, and more particularly to a reflectance spectroscope having a read head for minimizing singly-reflected light rays.
It is useful for various medical diagnostic purposes to utilize a reflectance spectroscope to analyze samples of body fluid, for example, to detect on immunotest strips or chemistry test strips the presence of blood in a person's urine. Conventional reflectance spectroscopes have been used to detect the presence of blood in a urine sample disposed on a reagent pad. Any blood present in the urine reacts with the reagent on the reagent pad, causing the reagent pad to change color to an extent which depends on the concentration of the blood. For example, in the presence of a relatively large concentration of blood, such a reagent pad may change in color from yellow to dark green.
One conventional reflectance spectroscope detects the concentration of the blood by illuminating the reagent pad and detecting, via a conventional reflectance detector, the amount of light received from the reagent pad, which is related to the color of the reagent pad. Based upon the magnitude of the reflectance signal generated by the reflectance detector, the spectroscope assigns the urine sample to one of a number of categories, e.g. a first category corresponding to no blood, a second category corresponding to a small blood concentration, a third category corresponding to a medium blood concentration, and a fourth category corresponding to a large blood concentration.
A prior art reflectance spectroscope has been provided with an optical system in the form of a read head in which a light bulb is disposed directly above the reagent pad to be tested and a reflectance detector is disposed at a 45.degree. angle to the horizontal surface of the reagent pad. Light from that spectroscope passes through a first vertical optical path from the illumination source to the reagent pad and through a second optical path, disposed 45.degree. with respect to the first optical path, from the reagent pad to the reflectance detector.
One problem with conventional reflectance spectroscopes is that light rays can be reflected from internal surfaces of the read head so that they are scattered in unintended directions, thus adversely affecting the accuracy of the spectroscope. Such unintended scattering of light rays may cause the reagent pad to be illuminated non-uniformly; it may cause areas adjacent the reagent pad to be illuminated which are not intended to be illuminated; and it may distort the distribution of light received by the reflectance detector from the reagent pad, thus adversely effecting the accuracy of the spectroscope.